It is common in many applications of electronic equipment to provide for electronic shielding. This shielding prevents or drastically reduces the transmission of electromagnetic signals to accomplish various purposes. For example, it may be desired to prevent the surreptitious detection of electromagnetic signals emitted by an electronic device. In this case, the electronic device is placed in a shielding cabinet. In other instances it is desirable to prevent the imposition of unknown electromagnetic radiation onto an electronic device. In this instance, the device is also placed in a shielding room or cabinet.
An electronically shielding cabinet is typically made of metal and includes metal components. If a room is employed, a metal screen is typically provided, and the door or windows are provided with gaskets to ensure electrical contact.
Typical gaskets include finger stock, made of a flexible metal, to provide spring-like fingers which are secured to one part of a cabinet or door jam of a room, while another part is engaged by the closed door. In another known gasket, the door jam or cabinet is provided with a double row of finger stock gasket material, and the door is provided with a wedge which is inserted between the rows of finger stock when the door is closed.
The double row of finger stock gasket is more reliable and has uniform attenuation because the spring pressures are equalized. This type of arrangement, however, requires a mechanism to assist in opening and closing a door of any substantial size because of the force required to urge the wedge between the gaskets. In one known mechanism, a door has a vertically movable cam follower which engages a sloped cam on an edge of the cabinet. As the cam follower is urged upwardly, it rides along the cam to pull the door closed. The cam follower is operated by a push rod which is connected to a disk rotated by a handle. This design is popular because a rotating handle shaft is easily electrically sealed by the use of round bushings with controlled tolerances. The disadvantage, however, is that the handle must be large to obtain an adequate mechanical advantage. Moreover, the mechanism has a large requirement for operational space, and often interferes with the placement of windows to allow viewing of the interior of the room or cabinet.
Other arrangements for rooms or cabinets not provided with electromagnetic shielding are known. U.S. Pat. No. 2,745,132 (Clark et al.) shows a refrigerator wherein a door carries a latch mechanism which comprises a pivotable latch bolt operated by a linearly-movable actuating link. The latch bolt engages a stud attached to a swinging leaf of a hinge. The linearly moving actuating link is operated by a crank operated from a central, rotational handle located in the middle of the door.
Other door latches are shown in U.S. Pat. Nos. 1,554,700 (Anderson), 1,529,085 (Preble), 1,923,903 (Albach et al.), 2,130,302 (Henderson), 3,413,025 (Sperry), and 3,882,291 (Chiboroski).